29 Aug
2002
29 Aug
'02
1:04 p.m.
--- Tony Duell <ard(a)p850ug1.demon.co.uk> wrote:
You mean you can actually buy them as loose chips? You have better PC
shops that we do....
I doubt it, especially now that modern motherboards have integrated
the keyboard interface.
I did not mean to suggest that you could ever buy one loose, but if
you brought your machine in for service, that would be how they described
where the fault was if the keyboard didn't respond... i.e., "your
keyboard BIOS is fried."
I am not sure where the term 'keyboard BIOS'
came from, but it can go
back there :-)
I know it's a pre-programmed microcontroller, but in the U.S., if you
go to a PeeCee shop, that is what they call it. I assume you also realise that the 8042 outputs PC
keyboard scan codes,
and it's up to you to translate them into characters. This can be done in
hardware (using an EPROM as a lookup table, and some logic to handle
shift/control (you have to detect those scancodes and set/clear
flip-flops for the shift/control status). It's possible, but not trivial.
That was the idea - a translator ROM.
Of course there _are_ keyboards with plain async
outputs [1] which would
trivially link to the receiver side of your UART, but they are a lot less
common than the PC/AT one.
[1] Obvious examples : PERQ 2 keyboard, Xerox Daybreak keyboard, DEC
LK201. You'd have to do a bit of hardware interfacing to convert signal
levels, of course...
The LK201 emits ASCII not scan codes? Cool. I can handle that (or did
you just mean async characters at a reasonable baud rate?) I guess
I'll have to track down the docs to them. Converting the signal levels
is no big shake.
Thanks,
-ethan
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